All Sky Camera Revisited

[Gina]

Can't find the exact part number for the Peltier TEC but I see I bought it from RS-online and it's about 15v and 40mm x 40mm drawing about 3A at 13.8v.

[Gina]

Checked my account with rs-online.com and found it.  Ordered October last year.

[CedricTheBrave]

30 minutes ago, Gina said:

Checked my account with rs-online.com and found it.  Ordered October last year.

Thank you

[Gina]

I have started a Blog for this latest version of my ASC HERE with a parts list.

[Gina]

I'm keeping this thread going to consider ideas for improvements - the Blog will be for pretty much the final design.

I'm satisfied that the design is fine except for the possibility of the case leaking and damp (or worse) getting in.  This has always been a concern with cooling the camera below freezing to reduce image noise.  Ingress of moisture can cause two problems - condensation on optical surfaces or worse, ice melting during daytime and the water damaging the electronics.

I shall be using "indicating desiccant" where the colour changes from orange to dark green if it gets exhausted but apart from the top, the case is opaque ABS.  I looked for a transparent box but no joy.  It would be helpful if I could see the desiccant and know that the ASC insides were dry.  I've been thinking of how I could make the desiccant visible. 

Now to my latest thought...  How about a small glass jar with a lid that seals, with the lid glued and screwed to the bottom of the box and a hole through the lid and box to allow damp (or even water) to drain into the jar?  The jar would contain a sachet or two of desiccant and any colour change would be clear.  Also, if the desiccant became exhausted after time it could be replaced easily.

Edited May 10, 2020 by Gina

[DaveL59]

sounds interesting, one of those miniature jam jars perhaps, or the slightly larger ones that stores use for things like mint sauce?

Only risk there tho is the heat relaxing the grip of the lid and the jar working itself loose. Tho a strap under it might help retain it in place.

[Gina]

I'm looking at a Colman's Mustard jar about 3" high and 2" OD at the widest part at the bottom.

[DaveL59]

sounds better if its a screw on cap rather than a part twist type  

[Gina]

Yes, it's a full screw-on cap rather than part twist.  I was looking at a glass jar with metal part twist cap at first but thought it wasn't very secure.  The mustard jar is smaller too.

[DaveL59]

so long as the plastic cap can survive the temps and solar bleaching... that'd be the risk, that it gets brittle and fails.

Or thinking along the lines of a diseisil fuel/water filter...
https://www.ebay.co.uk/itm/UNIVERSAL-Chrome-Glass-Fuel-Petrol-Diesel-Inline-Filter-5-16-8mm/170953813596?hash=item27cda42e5c:g:XuMAAOSwV5tc2Te7

 

[Gina]

I can protect the cap with aluminium foil to keep the UV off it.  Also, the case of the ASC will shield it from direct sunlight.  I think I may also glue aluminium foil onto the ASC case to reflect UV.

[Gina]

I want to get the ASC finished and installed ASAP so I'm putting up with the less than pleasant appearance.   One day I hope to produce a nicer looking case that is airtight and partly transparent to show the state of the desiccant.  If I could find a humidity sensor that went down low enough I wouldn't need to see the desiccant.

[DaveL59]

it's certainly a nice to have, being able to check the sky any time and even remotely and of course your one gave such great star views at night too.

One day I might aspire to try to get closer to your image quality  

[Gina]

It does come at a cost unfortunately.

[DaveL59]

I bet your time has cost way more Gina  

But yes, all those gizzmos like 3D printer etc, hence I went the lazy route with an inverted CCTV PTZ dome that got used with non-functional camera and modified to suit - that's held up really well through all weather so far, it was the first small dome one that had the seal fail but some sealant and its back on the air again too. They were never designed to be used dome-upward of course  

[Gina]

Time doesn't cost me money though admittedly I don't know just how much of it I have.  I  could have saved time instead of money if I had used the ASI 183MC-PRO USB 3.0 Cooled Colour Camera at over £800 - the cheapest cooled astro camera that FLO sell AFAIK.  That would have saved all the cooling problems.  Of course I would have had to arrange that I got its cooling air from inside the observatory but at one stage I had a design for that.

Edited May 10, 2020 by Gina

[DaveL59]

😮 ouch!

but yes re time, problem we all face, unfortunately. Gotta admire your determination sticking with it and refining the designs tho Gina, its what inspired me to actually give it a go  

[Gina]

Good.

[DaveL59]

have to say though that all the post I've read on imaging, it's probably not a path I'll be following you along even tho am impressed at what you all capture  I'd like to take a few pics to show my daughter and grandaughter for sure, but I don't think I've the sort of time to be catching hours of data esp once work restarts. Not sure I'd be wanting to leave the scope out till all hours doing its thing either, the area is OK but there's a few dubious types around but you never know, one day...

Playing with the bridge camera again has got me thinking about a DSLR so I can put the old Minolta lenses to use again, which limits me to the Sony Alpha range, less supported in the astro side it seems. But looking at that if I go with an APS-C sensor the lenses would be limited too, so sell the old gear and buy from scratch, or get the Sony and a shorter FL lens to get the wide-angle range... Or really stretch and get the full-frame version as was the original plan 20 years ago. But then I think back to the days of lugging a camera bag with 3+ lenses etc and think maybe I'll just stick to the S100FS lol

Edited May 10, 2020 by DaveL59

[Gina]

Here is a screenshot of the camera image.  This is my living room ceiling and walls.  This is an exposure of 0.1s.  One thing is clear - the image from the lens is not central on the sensor and I'm losing some view at the top.  Maybe I can print an offset adapter to correct this.  The error appears to be about 0.5mm.

[DaveL59]

could the sensor board just be slightly offset when it was reinstalled?

[Gina]

No, it's located by the mounting screws.

[Gina]

I've put the camera on the guttering on the obsy ROR - here is the view - 8s exposure.  the view to the west is partly obscured by the roof.

[JamesF]

Is it possible that the living room image wasn't central because whatever the camera was resting on wasn't absolutely level, Gina?

James

Edited May 10, 2020 by JamesF

[Gina]

No, the lens is screwed into the camera body.